FDA rejects highly anticipated diet drug

WASHINGTON — Federal health regulators have decided not to approve an experimental diet pill called Qnexa, which had been touted by many experts as the most promising weight-loss drug in more than a decade.

The drug's maker, Vivus Inc., said in a statement Thursday that the Food and Drug Administration declined to approve the drug in its present form. The agency asked for more study results and additional information on its possible health risks, including major cardiovascular events and risks for women of childbearing potential.

The FDA did not ask for any new clinical studies, but more may be required if the agency's concerns aren't addressed, Vivus said.

"We remain confident in the efficacy and safety profile of Qnexa demonstrated in the clinical development program and look forward to continue working with the FDA towards the approval for the treatment of obesity," Vivus CEO Leland Wilson said in a statement.

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Vivus, based in Mountain View, Calif., is one of three small drugmakers racing to win approval for their weight-loss drugs. Many analysts picked Qnexa as the most promising contender because of the high level of weight loss reported in company studies: On average, patients lost more than 10 percent total body mass. That compared with weight loss of under 5 percent with drugs currently on the market, like Roche's Xenical.

But Qnexa's outlook took a significant hit in July, when a panel of experts assembled by the FDA voted 10-6 to not recommend the drug's approval. Panelists said the drug was associated with a number of dangerous side effects, including suicidal thoughts, heart palpitations, memory lapses and birth defects.

With rates of obesity and diabetes rising, doctors say new weight-loss drugs are needed, though the drug class has a history of safety issues.